/**
 *     __  ___
 *    /  |/  /___   _____ _____ ___   ____   ____ _ ___   _____
 *   / /|_/ // _ \ / ___// ___// _ \ / __ \ / __ `// _ \ / ___/
 *  / /  / //  __/(__  )(__  )/  __// / / // /_/ //  __// /
 * /_/  /_/ \___//____//____/ \___//_/ /_/ \__, / \___//_/
 *                                        /____/
 *
 * @description MessengerJS, a common cross-document communicate solution.
 * @author biqing kwok
 * @version 2.0
 * @license release under MIT license
 */
define(function(require, exports, module) {
    module.exports = (function(){

        // 消息前缀, 建议使用自己的项目名, 避免多项目之间的冲突
        var prefix = "arale-messenger",
            supportPostMessage = 'postMessage' in window;

        // Target 类, 消息对象
        function Target(target, name){
            var errMsg = '';
            if(arguments.length < 2){
                errMsg = 'target error - target and name are both required';
            } else if (typeof target != 'object'){
                errMsg = 'target error - target itself must be window object';
            } else if (typeof name != 'string'){
                errMsg = 'target error - target name must be string type';
            }
            if(errMsg){
                throw new Error(errMsg);
            }
            this.target = target;
            this.name = name;
        }

        // 往 target 发送消息, 出于安全考虑, 发送消息会带上前缀
        if ( supportPostMessage ){
            // IE8+ 以及现代浏览器支持
            Target.prototype.send = function(msg){
                this.target.postMessage(prefix + msg, '*');
            };
        } else {
            // 兼容IE 6/7
            Target.prototype.send = function(msg){
                var targetFunc = window.navigator[prefix + this.name];
                if ( typeof targetFunc == 'function' ) {
                    targetFunc(prefix + msg, window);
                } else {
                    throw new Error("target callback function is not defined");
                }
            };
        }

        // 信使类
        // 创建Messenger实例时指定, 必须指定Messenger的名字, (可选)指定项目名, 以避免Mashup类应用中的冲突
        // !注意: 父子页面中projectName必须保持一致, 否则无法匹配
        function Messenger(messengerName, projectName){
            this.targets = {};
            this.name = messengerName;
            this.listenFunc = [];
            prefix = projectName || prefix;
            this.initListen();
        }

        // 添加一个消息对象
        Messenger.prototype.addTarget = function(target, name){
            var targetObj = new Target(target, name);
            this.targets[name] = targetObj;
        };

        // 初始化消息监听
        Messenger.prototype.initListen = function(){
            var self = this;
            var generalCallback = function(msg){

                if(typeof msg == 'object' && msg.data){
                    msg = msg.data;
                }

                // 剥离消息前缀
                msg = msg.slice(prefix.length);

                for(var i = 0; i < self.listenFunc.length; i++){
                    self.listenFunc[i](msg);
                }
            };

            if ( supportPostMessage ){
                if ( 'addEventListener' in document ) {
                    window.addEventListener('message', generalCallback, false);
                } else if ( 'attachEvent' in document ) {
                    window.attachEvent('onmessage', generalCallback);
                }
            } else {
                // 兼容IE 6/7
                window.navigator[prefix + this.name] = generalCallback;
            }
        };

        // 监听消息
        Messenger.prototype.listen = function(callback){
            this.listenFunc.push(callback);
        };
        // 注销监听
        Messenger.prototype.clear = function(){
            this.listenFunc = [];
        };
        // 广播消息
        Messenger.prototype.send = function(msg){
            var targets = this.targets,
                target;
            for(target in targets){
                if(targets.hasOwnProperty(target)){
                    targets[target].send(msg);
                }
            }
        };

        return Messenger;

    })();
});